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Biomedical subjects

J Kucera

Publications and source records attributed to J Kucera.

At least 163 records · Page 9Linked to original sources
PubMed1984

Ultrastructure of extrafusal and intrafusal terminals of a (dynamic) skeletofusimotor axon in cat tenuissimus muscle.

Terminals of a histologically identified beta skeletofusimotor axon in cat tenuissimus muscle were examined in semi-thin (1 micrometer thick) and ultrathin transverse sections. The beta axon supplied one extrafusal endplate and two motor endings on the nuclear bag1 intrafusal muscle fiber. The staining properties of the co-innervated bag1 and extrafusal fibers were dissimilar. The beta intrafusal and extrafusal terminals were also dissimilar by both light and electron microscopy , differing in length, mitochondrial content of the sole-plate, and folding of the post-synaptic membrane.

Animals↗
PubMed1984

Nonselective motor innervation of nuclear bag1 intrafusal muscle fibers in the cat.

The motor nerve supply to cat nuclear bag1 intrafusal muscle fibers was reconstructed from light and electron microscopy of serial transverse sections of spindles in the tenuissimus muscle. Twenty-six of thirty poles of bag1 fibers that were examined received motor innervation. Every innervated bag1 pole received at least one (range 1-3) selective motor axon that supplied this fiber type only. Four of the innervated bag1 poles (15%) received additional motor supply from a nonselective motor axon that also innervated one nuclear chain fiber in the same spindle pole. The chain fibers co-innervated with bag1 fibers were among the longest chain fibers although they were shorter than two long chain fibers also present in the spindle poles. In cross-sections stained with toluidine blue they displayed 1-3 equatorial nuclei side by side, and there were fewer intermyofibrillar granules in their polar regions than in most of the other chain fibers. The endings of nonselective motor axons on the bag1 and chain fibers were morphologically and ultrastructurally dissimilar. It is suggested that instances of common innervation of the (dynamic) bag1 fiber and a (static?) chain fiber represent an integral and, presumably, functionally meaningful part of the motor pattern in some cat spindles.

Animals↗
PubMed1984

Ultrastructure of dynamic and static skeletofusimotor endings in a cat muscle spindle.

Endings of four beta skeletofusimotor axons in a spindle of the cat tenuissimus muscle were examined in semithin (1-micron thick) and ultrathin transverse serial sections. Two (dynamic) beta axons terminated on the nuclear bag1 intrafusal muscle fiber and on extrafusal fibers of the dark type. Two (static) beta axons terminated on the nuclear chain intrafusal fibers and extrafusal fibers of the intermediate type. The degree of indentation of axon terminals into the muscle surface, thickness of the sole plate and extent of folding of subjunctional membranes differed among intrafusal and extrafusal terminations of the same axon. Endings of beta axons on the bag1 and chain fibers were also morphologically dissimilar. Motor axons may not determine ending morphology. Rather the form and structure of a beta bag1 or chain ending may be determined by the type of intrafusal fiber on which the ending lies and the ending's distance from the primary sensory axon.

Animals↗
PubMed1984

Nonselective motor innervation of intrafusal fibers in muscle spindles of the rat.

Distributions of motor axons to different types of intrafusal fiber were reconstructed from serial 1-micron thick transverse sections of six poles of muscle spindle in the rat soleus. Motor axons innervated (dynamic) bag1 fibers, or (static) bag2 fibers in conjunction with chain fibers. However, approximately forty percent of axons that supplied the spindles synapsed on both bag1 and bag2 or bag1 and chain fibers. The significance of this co-innervation of dynamic and static intrafusal fibers is discussed relative to the general organization and function of mammalian spindles.

Animals↗
PubMed1983

Ultrastructural study of motor endings on long chain intrafusal fibers in muscle spindles of the cat.

Five complete poles of long nuclear chain intrafusal fibers of cat tenuissimus muscle spindles embedded in a plastic medium were cut in serial, 1 micron thick transverse sections and stained with toluidine blue. Each fiber pole displayed one plate-type motor ending positioned outside the encapsulated part of the spindle. Ultrastructurally, the endings resembled extrafusal end-plates and were more complex, in terms of prominence of sole-plate and degree of post-junctional folding, than any other motor ending present in the spindles. They were identified as the terminals of static (fast) skeletofusimotor axons, which preferentially innervate the longest nuclear chain fibers of cat spindles.

Animals↗